This invention pertains to an electromagnetic read/write head for perpendicular reading and writing, and more particularly, to what is referred to as a probe or single pole head.
Conventional probe heads for perpendicular recording (reading/writing) may be made by fabricating the coil and thin-film pole and yoke structure on a ferrite body which functions both as a magnetic return structure and as an air-bearing structure. Alternatively, a plated or otherwise deposited high permeability alloy layer may serve as the magnetic return structure. The coil or coils in such a head typically reside in a body of insulative material, such as hard-baked photoresist, and following formation of the coils in this body of material, a pole and yoke structure is formed over the insulated coil structure by plating a high permeability magnetic alloy, e.g., nickel-iron, through a patterned photoresist mask.
One problem with what has just been described is that the surface of the insulated coil structure is non-planar, since the hard-baked photoresist must not extend to the tip of the pole and the air bearing surface where it would lead to unreliable mechanical operation. Such a non-planar surface presents severe problems, especially for high topography multilayer coil structures, in precisely patterning the pole and yoke because the photomask is not everywhere in contact with the photoresist during exposure, and the resulting Fresnel diffraction leads to pattern distortion. This distortion becomes particularly troublesome as the width of the pole tip is made smaller, i.e., as the track density capability of the head increases.
A second and equally serious consequence of the nonplanar nature of the substrate on which the pole and yoke are fabricated has to do with the sensitivity of the magnetic properties of thin magnetic films to the texture and topography of the surface on which such films are formed, as well as the thermal and chemical stability of the substrate during subsequent annealing or thermal cycling. In general, the smoother and the flatter the substrate, and the less stress resulting from thermal cycling, the easier it is to create patterned magnetic films with excellent soft magnetic properties. The fact that the pole tip must be formed on a suitable inorganic surface (for reasons stated above) while the yoke is formed on the surface of an organic material is a concern when considering the widely different coefficients of expansion of the materials.
A general object of the present invention is to avoid the problems which attend the preparation of such a pole structure over uneven territory.
More particularly, an important object of the invention is to provide a highly polished, planarized inorganic surface on which to form the pole and yoke structure so as completely to avoid the topographical and materials incompatibility problems discussed above.
For the purposes of illustration herein, two different embodiments of a head formed in accordance with the invention are disclosed, in one of which the coil is embedded in a body of hard-baked photoresist, and in the other of which, the coil is formed in an inorganic material such as aluminum oxide.
The various important features and offered advantages of the invention (structure and method) will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawings.